diff --git a/src/gateway/server-chat.ts b/src/gateway/server-chat.ts
index ef390114ef0..baca779f231 100644
--- a/src/gateway/server-chat.ts
+++ b/src/gateway/server-chat.ts
@@ -11,12 +11,33 @@ import {
   resolveMergedAssistantText,
   shouldSuppressAssistantEventForLiveChat,
 } from "./live-chat-projector.js";
+import type {
+  ChatRunState,
+  SessionEventSubscriberRegistry,
+  ToolEventRecipientRegistry,
+} from "./server-chat-state.js";
 import { loadGatewaySessionRow } from "./server-chat.load-gateway-session-row.runtime.js";
 import { persistGatewaySessionLifecycleEvent } from "./server-chat.persist-session-lifecycle.runtime.js";
 import { deriveGatewaySessionLifecycleSnapshot } from "./session-lifecycle-state.js";
 import { loadSessionEntry } from "./session-utils.js";
 import { formatForLog } from "./ws-log.js";
 
+export {
+  createChatRunRegistry,
+  createChatRunState,
+  createSessionEventSubscriberRegistry,
+  createSessionMessageSubscriberRegistry,
+  createToolEventRecipientRegistry,
+} from "./server-chat-state.js";
+export type {
+  ChatRunEntry,
+  ChatRunRegistry,
+  ChatRunState,
+  SessionEventSubscriberRegistry,
+  SessionMessageSubscriberRegistry,
+  ToolEventRecipientRegistry,
+} from "./server-chat-state.js";
+
 function resolveHeartbeatAckMaxChars(): number {
   try {
     const cfg = getRuntimeConfig();
@@ -84,307 +105,12 @@ function normalizeHeartbeatChatFinalText(params: {
   return { suppress: false, text: stripped.text };
 }
 
-export type ChatRunEntry = {
-  sessionKey: string;
-  clientRunId: string;
-};
-
-export type ChatRunRegistry = {
-  add: (sessionId: string, entry: ChatRunEntry) => void;
-  peek: (sessionId: string) => ChatRunEntry | undefined;
-  shift: (sessionId: string) => ChatRunEntry | undefined;
-  remove: (sessionId: string, clientRunId: string, sessionKey?: string) => ChatRunEntry | undefined;
-  clear: () => void;
-};
-
-export function createChatRunRegistry(): ChatRunRegistry {
-  const chatRunSessions = new Map<string, ChatRunEntry[]>();
-
-  const add = (sessionId: string, entry: ChatRunEntry) => {
-    const queue = chatRunSessions.get(sessionId);
-    if (queue) {
-      queue.push(entry);
-    } else {
-      chatRunSessions.set(sessionId, [entry]);
-    }
-  };
-
-  const peek = (sessionId: string) => chatRunSessions.get(sessionId)?.[0];
-
-  const shift = (sessionId: string) => {
-    const queue = chatRunSessions.get(sessionId);
-    if (!queue || queue.length === 0) {
-      return undefined;
-    }
-    const entry = queue.shift();
-    if (!queue.length) {
-      chatRunSessions.delete(sessionId);
-    }
-    return entry;
-  };
-
-  const remove = (sessionId: string, clientRunId: string, sessionKey?: string) => {
-    const queue = chatRunSessions.get(sessionId);
-    if (!queue || queue.length === 0) {
-      return undefined;
-    }
-    const idx = queue.findIndex(
-      (entry) =>
-        entry.clientRunId === clientRunId && (sessionKey ? entry.sessionKey === sessionKey : true),
-    );
-    if (idx < 0) {
-      return undefined;
-    }
-    const [entry] = queue.splice(idx, 1);
-    if (!queue.length) {
-      chatRunSessions.delete(sessionId);
-    }
-    return entry;
-  };
-
-  const clear = () => {
-    chatRunSessions.clear();
-  };
-
-  return { add, peek, shift, remove, clear };
-}
-
-export type ChatRunState = {
-  registry: ChatRunRegistry;
-  rawBuffers: Map<string, string>;
-  buffers: Map<string, string>;
-  deltaSentAt: Map<string, number>;
-  /** Length of text at the time of the last broadcast, used to avoid duplicate flushes. */
-  deltaLastBroadcastLen: Map<string, number>;
-  abortedRuns: Map<string, number>;
-  clear: () => void;
-};
-
-export function createChatRunState(): ChatRunState {
-  const registry = createChatRunRegistry();
-  const rawBuffers = new Map<string, string>();
-  const buffers = new Map<string, string>();
-  const deltaSentAt = new Map<string, number>();
-  const deltaLastBroadcastLen = new Map<string, number>();
-  const abortedRuns = new Map<string, number>();
-
-  const clear = () => {
-    registry.clear();
-    rawBuffers.clear();
-    buffers.clear();
-    deltaSentAt.clear();
-    deltaLastBroadcastLen.clear();
-    abortedRuns.clear();
-  };
-
-  return {
-    registry,
-    rawBuffers,
-    buffers,
-    deltaSentAt,
-    deltaLastBroadcastLen,
-    abortedRuns,
-    clear,
-  };
-}
-
-export type ToolEventRecipientRegistry = {
-  add: (runId: string, connId: string) => void;
-  get: (runId: string) => ReadonlySet<string> | undefined;
-  markFinal: (runId: string) => void;
-};
-
-export type SessionEventSubscriberRegistry = {
-  subscribe: (connId: string) => void;
-  unsubscribe: (connId: string) => void;
-  getAll: () => ReadonlySet<string>;
-  clear: () => void;
-};
-
-export type SessionMessageSubscriberRegistry = {
-  subscribe: (connId: string, sessionKey: string) => void;
-  unsubscribe: (connId: string, sessionKey: string) => void;
-  unsubscribeAll: (connId: string) => void;
-  get: (sessionKey: string) => ReadonlySet<string>;
-  clear: () => void;
-};
-
-type ToolRecipientEntry = {
-  connIds: Set<string>;
-  updatedAt: number;
-  finalizedAt?: number;
-};
-
-const TOOL_EVENT_RECIPIENT_TTL_MS = 10 * 60 * 1000;
-const TOOL_EVENT_RECIPIENT_FINAL_GRACE_MS = 30 * 1000;
 /**
  * Keep this aligned with the agent.wait lifecycle-error grace so chat surfaces
  * do not finalize a run before fallback or retry reuses the same runId.
  */
 const AGENT_LIFECYCLE_ERROR_RETRY_GRACE_MS = 15_000;
 
-export function createSessionEventSubscriberRegistry(): SessionEventSubscriberRegistry {
-  const connIds = new Set<string>();
-  const empty = new Set<string>();
-
-  return {
-    subscribe: (connId: string) => {
-      const normalized = connId.trim();
-      if (!normalized) {
-        return;
-      }
-      connIds.add(normalized);
-    },
-    unsubscribe: (connId: string) => {
-      const normalized = connId.trim();
-      if (!normalized) {
-        return;
-      }
-      connIds.delete(normalized);
-    },
-    getAll: () => (connIds.size > 0 ? connIds : empty),
-    clear: () => {
-      connIds.clear();
-    },
-  };
-}
-
-export function createSessionMessageSubscriberRegistry(): SessionMessageSubscriberRegistry {
-  const sessionToConnIds = new Map<string, Set<string>>();
-  const connToSessionKeys = new Map<string, Set<string>>();
-  const empty = new Set<string>();
-
-  const normalize = (value: string): string => value.trim();
-
-  return {
-    subscribe: (connId: string, sessionKey: string) => {
-      const normalizedConnId = normalize(connId);
-      const normalizedSessionKey = normalize(sessionKey);
-      if (!normalizedConnId || !normalizedSessionKey) {
-        return;
-      }
-      const connIds = sessionToConnIds.get(normalizedSessionKey) ?? new Set<string>();
-      connIds.add(normalizedConnId);
-      sessionToConnIds.set(normalizedSessionKey, connIds);
-
-      const sessionKeys = connToSessionKeys.get(normalizedConnId) ?? new Set<string>();
-      sessionKeys.add(normalizedSessionKey);
-      connToSessionKeys.set(normalizedConnId, sessionKeys);
-    },
-    unsubscribe: (connId: string, sessionKey: string) => {
-      const normalizedConnId = normalize(connId);
-      const normalizedSessionKey = normalize(sessionKey);
-      if (!normalizedConnId || !normalizedSessionKey) {
-        return;
-      }
-      const connIds = sessionToConnIds.get(normalizedSessionKey);
-      if (connIds) {
-        connIds.delete(normalizedConnId);
-        if (connIds.size === 0) {
-          sessionToConnIds.delete(normalizedSessionKey);
-        }
-      }
-      const sessionKeys = connToSessionKeys.get(normalizedConnId);
-      if (sessionKeys) {
-        sessionKeys.delete(normalizedSessionKey);
-        if (sessionKeys.size === 0) {
-          connToSessionKeys.delete(normalizedConnId);
-        }
-      }
-    },
-    unsubscribeAll: (connId: string) => {
-      const normalizedConnId = normalize(connId);
-      if (!normalizedConnId) {
-        return;
-      }
-      const sessionKeys = connToSessionKeys.get(normalizedConnId);
-      if (!sessionKeys) {
-        return;
-      }
-      for (const sessionKey of sessionKeys) {
-        const connIds = sessionToConnIds.get(sessionKey);
-        if (!connIds) {
-          continue;
-        }
-        connIds.delete(normalizedConnId);
-        if (connIds.size === 0) {
-          sessionToConnIds.delete(sessionKey);
-        }
-      }
-      connToSessionKeys.delete(normalizedConnId);
-    },
-    get: (sessionKey: string) => {
-      const normalizedSessionKey = normalize(sessionKey);
-      if (!normalizedSessionKey) {
-        return empty;
-      }
-      return sessionToConnIds.get(normalizedSessionKey) ?? empty;
-    },
-    clear: () => {
-      sessionToConnIds.clear();
-      connToSessionKeys.clear();
-    },
-  };
-}
-
-export function createToolEventRecipientRegistry(): ToolEventRecipientRegistry {
-  const recipients = new Map<string, ToolRecipientEntry>();
-
-  const prune = () => {
-    if (recipients.size === 0) {
-      return;
-    }
-    const now = Date.now();
-    for (const [runId, entry] of recipients) {
-      const cutoff = entry.finalizedAt
-        ? entry.finalizedAt + TOOL_EVENT_RECIPIENT_FINAL_GRACE_MS
-        : entry.updatedAt + TOOL_EVENT_RECIPIENT_TTL_MS;
-      if (now >= cutoff) {
-        recipients.delete(runId);
-      }
-    }
-  };
-
-  const add = (runId: string, connId: string) => {
-    if (!runId || !connId) {
-      return;
-    }
-    const now = Date.now();
-    const existing = recipients.get(runId);
-    if (existing) {
-      existing.connIds.add(connId);
-      existing.updatedAt = now;
-    } else {
-      recipients.set(runId, {
-        connIds: new Set([connId]),
-        updatedAt: now,
-      });
-    }
-    prune();
-  };
-
-  const get = (runId: string) => {
-    const entry = recipients.get(runId);
-    if (!entry) {
-      return undefined;
-    }
-    entry.updatedAt = Date.now();
-    prune();
-    return entry.connIds;
-  };
-
-  const markFinal = (runId: string) => {
-    const entry = recipients.get(runId);
-    if (!entry) {
-      return;
-    }
-    entry.finalizedAt = Date.now();
-    prune();
-  };
-
-  return { add, get, markFinal };
-}
-
 export type ChatEventBroadcast = (
   event: string,
   payload: unknown,